The Department of Health is preparing the ground for a possible roll-out of a cheap, but unlicensed drug which can help prevent older people going blind, as NHS bills for an approved but much more costly drug soar.

Avastin does have a licence, but as a treatment for bowel cancer. However, in the United States and across the rest of the world it has increasingly been used – split into tiny doses and injected into the eye – to stop people going blind from wet age-related macular degeneration (AMD), the commonest cause of blindness.

The manufacturers of Avastin, US-based Genentech, have resisted this use of their drug. They produce Lucentis, which was derived from Avastin, but is made in the right-size doses. It can cost as much as 100 times the price of an Avastin injection.

Lucentis was put through clinical trials and received a licence and was then assessed for cost-effectiveness by the National Institute for Health and Clinical Excellence (Nice).

Nice had reservations about the price, which is £761.20 an injection, or £10,700 for a year's course of 14 injections, but after an offer by Novartis, which markets the drug in Britain, to pay for treatment after 14 injections, Nice agreed in 2008 that the NHS should routinely use it.

The bill to the NHS, however, has been higher than expected, as thousands of people flock for treatment – and stay on it longer than expected. There are 26,000 new cases of wet AMD in Britain every year. Normally, Nice assesses only licensed drugs, but the Department of Health has now asked it to consider assessing Avastin for eyes.

The department "has asked Nice to explore with stakeholders what value we can add in advising the NHS on the clinical and cost effectiveness of Avastin (bevacizumab) to treat wet age-related macular degeneration, the leading cause of blindness in the UK," Nice said in a statement.

The move is likely to upset the drug companies and send a shot across the bows of an industry frequently criticised for high prices. The government has already shown interest in the cheaper drug by funding a head-to-head trial of Lucentis and Avastin in wet AMD. The industry has been critical of the trial, called IVAN,claiming it is badly designed and of poor quality.

But the Macular Disease Society gave a cautious welcome to the idea of a Nice review. "We have quite a lot of anecdotes from around the country not just associated with the cost of Lucentis but the pressure on services because of the sheer numbers of people," said Cathy Yelt. "There are more people in the system having treatment than was originally foreseen."

It had been expected that many people would have only a few injections and then stabilise, or die of old age or give up on the treatment, but that had not proved to be the case. In some areas people were having trouble accessing treatment – one woman could only get treatment for both eyes by going to two different clinics. "Everybody has been caught by surprise by the numbers," she said.

Richard Smith, vice president of the Royal College of Ophthalmologists, said they had called on several occasions for trials to compare the drugs. "Our paramount concern is the safety of patients and it is reasonable for the Department of Health to examine whether there are safe, efficacious and cost-effective alternatives to existing treatments," he said.

"Whatever the motivation of the review, any conclusions drawn from it should be entirely based on firm scientific evidence of safety and efficacy."

The Royal National Institute for the Blind, which has funding from Novartis and campaigned for the introduction of Lucentis, had reservations. "As we don't have further details at this time, we are cautious in our response," said Steve Winyard, head of policy and campaigns.

"However, RNIB would be greatly concerned by any steps that could undermine the current regulatory system, which is rightly based on assessing clinical evidence, primarily from randomised-control trials. This level of investigation ensures any treatments that are subsequently approved have been shown to be safe and effective."